This would be ABSOLUTE CINEMA
Since it seems to have a ton of "Bonnie and Clyde" elements into the game story, and the multiple protagonists in GTA V really worked, they probably are going to focus much more into this game mechanic (I hope so) and create a history where the character changes is really present into it
+
Multiple ways/choices can be really reachable nowadays and, for me, is NEEDED in this kind of sandbox games, cuz they're give you more and more freedom... not having it it's ok, but this gives a HUGE upgrade into the imersion and storytelling. Imagine how many series you can watch from different Youtubers/streamers and everyone of them have a different ending from YOURS)
Exactly the game should actually feel like anything's possible...and there could be several different unique ways to complete a mission and each action should be able to have a different outcome to the story...like this element will set GTA 6 apart from the rest and truly be worth to make another GTA otherwise GTA 5 is still pretty good and there won't be actual reason to make another one....don't get me wrong Rockstar's story has always been good but this element will take it to next level